1. Field of the Invention
The invention is based on an internal gear pump for a brake system of the kind used particularly in the hydraulic system of vehicle brake systems.
2. Description of the Prior Art
An internal gear pump which can generate a suitably high pressure level of the fluid is already disclosed in German Patent Disclosure DE 196 13 833 B4. Here, the fluid is pumped in the usual way from the suction side to the compression side of the internal gear pump because a filler piece, tapering toward the compression side, is disposed in a crescent-shaped annular chamber of the pump, between the ring gear and the pinion, and is braced by one end axially against the fluid pressure on the compression side at a stop face. The filler piece rests with its curved inner and outer circumferential surface on the pinion and ring gear, respectively, with radial sealing at a plurality of tooth tips. Since the fluid volumes entrained by the sealed-off tooth gaps of the gear wheels that are rotating in the same direction are united at the tapered end of the filler piece, the desired high pressure level results in this region of the pump. To achieve the most effective possible sealing off of the tooth gaps in the region of the tooth tips, the filler piece is assembled from a segment holder, forming the base part, and a sealing segment, braced movably on the segment holder, and the circumferential surface of the segment holder rests on the covered tooth tips of the pinion, and the opposed circumferential surface of the sealing segment rests on the covered tooth tips of the ring gear. Between the segment holder and the sealing segment, a leaf spring arrangement with three leaf springs is also braced, by means of which the segment holder and sealing segment are forced apart and are thus subject to a spring load at the covered tooth tips. In addition, under suitable operating conditions, the segment holder and sealing segment are forced apart via a fluid pressure corresponding to approximately half the operating pressure, since an interstice between the segment holder and the sealing element, which is partitioned off by elastic sealing rollers of an elastomer or polymer material, communicates fluidically through recesses with a pressure buildup region of the ring gear. The sealing rollers engage an associated groove, and during the shifting of the sealing element, they must each be held in their sealing position by a respective one of the three leaf springs. Thus the sealing between the covered tooth tips and the circumferential side, cooperating with them, of the segment holder and sealing element automatically remains effective as the pressure level of the pump rises from an increase in the contact pressure. The individual parts of the filler piece, however, must be manufactured with high precision in order to ensure perfect function of the internal gear pump over an appropriate length of service.